Legacy embedded systems, networks, and fieldbus architectures for factory automation, heating ventilation and air conditioning (HVAC) control, building automation, transportation, and other applications have relied on publish-subscribe (pub-sub) messaging methods to achieve highly scalable networks (having many nodes) while also guaranteeing timely message delivery for automation and control applications. Historically, control networks have been supplied by proprietary, vertically integrated vendors and have been isolated from corporate backbone networks and the Internet. Such isolation has benefited security by providing physical separation between control networks (which place a high value on safe operation) and backbone/Internet networks that are largely exposed to malware and a variety of miscreant attacks. However, as Internet of things (IoT) technology becomes more prevalent, pub-sub messaging infrastructure of legacy networks will be more complex and insecure.